Polyimide resins have outstanding thermal resistance and solvent stability, as well as good mechanical strength and tensile properties. They are used in a wide range of areas such as photographic films, insulation materials for electrical equipment, carrier tapes, and heat-insulating laminating materials in aircraft and spaceships. They are also used as the matrix resin in varnish, tape, adhesives and fiber reinforced composite materials.
Current research and development work attempts to create new types of polyimides that have advantages in addition to the known polyimide properties. In particular polyimide materials which can be used to make films having excellent adhesive properties to copper and other polyimides would be extremely useful in many high temperature applications. As an example, a block copolymer of copolyimide obtained by polycondensation of 3,3′,4,4′ Biphenyltetracarboxylic dianhydride (BPDA) and p-Phenylenediamine (PDA) is often employed in electronic parts used in applications needing high mechanical strength and resistance to high temperatures. However, its adhesive strength to copper or other polyimides, which are often used in electronics, is rather poor. This often results in the peeling of a copolyimide film and reduced life of an electronic part. Many patents have been issued relating to this kind of polyimide, but none of them have solved the problem of poor adhesive strength.